Apparatus for controlling acidulated bath



April 9, 1968 A. DOUTY ET A1.

APPARATUS FOR CONTROLLING ACIDULATED BATH Filed sept. 1, 1965 4Sheets-Sheet l INVENTORS M wh@ ATTORNEYS April 9, 1968 A. DoUTY ET Al.3,376,883

APPARATUS FOR CONTROLLING ACIDULATED BATH Filed Sept. l, 1965 4Sheets-Sheet 2 INVENTORS I 95 ATTORNEYS April 9, 196s Filed sept. l,I

A. DOUTY ET AL APPARATUS FOR CONTROLLING ACIDULATED BATH 4 Sheets-Sheet5 fr L) A T TOR/V5 ys l April 9, 1968 A. DoUTY ET AL 3,376,883

APPARATUS FOR CONTROLL'ING ACIDULATED BATH Filed Sept. l, 1965 4Sheets-Sheet 4 INVENTORS awa@ A 7 TOR/VE YS United States Patent3,376,883 APPARATUS FOR CONTROLLING ACHDULATED BATH Alfred Douty,Wyucote, Dwight E. Buczkowski, Oreland, and James W. Harrison, Wyndmoor,Pa., assignors to Amchem Products, Inc., Ambler, Pa., a corporation ofDelaware Filed Sept. 1, 1965, Ser. No. 484,254

7 Claims. (Cl. 137-88) ABSTRACT OF THE DISCLOSURE Apparatus is providedfor automatically controlling an acidulated rinse bath for treatingmetal, which includes equipment for introducing concentrated activechemicals to the bath in coaction with equipment for introducing waterfor the bath, the equipment being controlled by switching means. Theswitching means are actuated directly or indirectly by closure of one ormore of a group of three initiating switches, and the three initiatingswitches are respectively operated by a recycling proportional timer, aconductance sensitive relay in conjunction with a conductivity cell, anda level sensing device.

This invention relates to the art of coating metal surfaces. Moreparticularly, it relates to the application of an acidulated rinse overmetal surfaces which already have been subjected to the action ofconventional phosphate coating solutions.

More specifically, the invention relates to the provision of a simple,novel and relatively inexpensive method and apparatus for automaticallymaintaining such an acidulated rinsing solution in optimum condition.

Before ldescribing the objects and advantages of the present invention,it will be helpful to consider certain prior art practices as employedin the rinsing of chemical conversion coatings on metal surfaces.

In general, it is known that modern-day phosphate coating orphosphatizing is done in a sequence of events i.e., clean, water rinse,phosphate coat, water rinse, and chemical rinse, i.e., acidulated rinse.The present invention, while relating to the final acidulated rinse,does S in a sequence of phosphatizing wherein an intermediate waterrinse is used after phosphatizing and before the final chemical rinse.

In order more fully to achieve optimum corrosion resistance and paintadhesion properties of phosphate coated metal surfaces, it is desirableto rinse such phosphated surfaces with dilute, acidulated solutionscontaining hexavalent chromium ions and/or phosphoric acid. One of theearlier patents teaching the use of acidulated rinsing solution overphosphate coated metal surfaces is U.S. Patent No. 2,403,126, wherein itis taught that the acidulated rinsing solution may contain from l to 16ozs; of chromic acid (Cros) per 100 gallons of solution, and that suchrinsing solution be maintained at a pH of 2.0 to 4.6.

It was subsequently recognized that enhanced corrosion resistance couldbe obtained if the acidulated rinsing solutions had dissolved thereinother ionic components, such as, for example, nitrite ion, which istaught in German Patent No. 896,892.

However, such acidulated rinsing solutions, even though very dilute,'are sutliciently acidic to dissolve portions of the phosphate coatingand thereby to accumulate dissolved ionic constituents in the rinsingsolutions. Attempts have been made to reduce or minimize the dissolutionof the phosphate coatings by incorporating into the rinsing solutionssuficient cationic constituents so as to preclude the presence of freeacid through use of am 3,376,883 Patented Apr. 9, 1968 ice monium ions,as taught in U.S. Patent No. 2,634,225, or polyvalent metal ions such asCa, Cd, Al and/or Zn, as taught in French Patent No. 1,141,925.

Moreover, it has recently been found that solutions of admixtures ofchromium compounds, including both hexavalent chromium and reduced formsthereof, provide enhanced corrosion resistance when employed aS rinsesover phosphate coated metal surfaces. Such teachings are found in U.S.Patent No. 3,063,877.

During continuous operation of all of these prior art acidulated rinsingsolutions, the salt concentration thereof increases through dragged-insalt contaminan-ts from the water rinse and also as a result ofevaporation. Frequently, this salt build-up will continue until a pointisv reached Where the acidulated rinsing action no longer imparts anyimprovement in corrosion resistance, but actually results in reducedcorrosion resistance so far as salt spray and humidity tests areconcerned.

Various attempts have -been made to overcome this problem of increasedionic concentration in acidulated final rinsing baths. For example,frequent discard of used solutions and replacement thereof with freshbaths has been adopted in some installations, but while this pro- Cedureresults in completely satisfactory rinsing lof the' coated metalsurfaces, it also creates a serious production bottleneck, particularlyin' high speed production, such, for example, as strip line operations.

During operation of these acidulated rinses, several changes tend tooccur in their composition. These chan-ges and their causes are asfollows:

(l) Depletion of the desirable ingredients, such aS chromic acid,phosphoric acid, etc., which will hereinafter be called activeingredients.

The causes of this depletion in order portance and frequency ofoccurrence are: (a) Drag-out of the solution by adherence to, or byentrapment in undrained hollowsof the work.

(b) Overflow of the solution because of water not containing activeingredients being dragged in orv otherwise introduced into the solutionwith a consequent increase in the solution volume.

(c) Chemical action of the solution on the coating on metal. This isgenerally rather unimportant -as a de` pleting influence but may resultin some increase in the amount of undesirable constituents in thesolution.

(2) Accumulation of undesirable ingredients, especially ionicimpurities.

This may be the result of (a) Dragged in stages. This source ofcontamination of the acidulated rinse is minimized by providing a priorrinse in overflowing water. Nevertheless, hollow objects are rarelyperfectly drained and thus bring into the acidulated rinse considerableamounts of water and remove equivalent amounts of the it certain thatthe dragged in water is contaminated, for example, with the phosphatecoating solution itself. Drag-in and drag-out thus cause bothcontamination and depletion of the'acidulated rinsing solution.

(b) Chemical action of the metal. This again can be by suitable choiceof the erties of the solution.

(c) Partial evaporation of the rinsing solution, which in turn leads toa concentration of the impurities in the fresh water used to make up andreplenish the' solution itself. Though not usually very important, thiseffect may become appreciable when the acidulated rinsing solution isheated to facilitate drying of the emerging metal surfaces.

pH or other chemical prop- It has been customary toV deal with the aboveeffects vwhich tend to occur in these solutions by one of several ofdecreasing imsolution from previous processingl solution. This effect,too makes.

acidulated rinse on the cooledy minimized but not eliminated means.First or all, any change in solution level has been dealt with by meansof a water supply valve actuated by a float or by other means sensitiveto solution level. Addition of water in this manner (or any other), ineither larger or smaller amounts to the acidulated rinse solution tank,results in an ultimate dilution of the solution in both activeingredients and in impurities.

Restoration of depletion of active ingredient was usually accomplishedeither by occasional manual addition or by continual pumping from acontainer of concentrated active material, the solution concentrationbeing checked by occasional chemical analysis as by titration and thereplenishing additions being accordingly altered.

Accumulation of undesired impurities was usually overcome byperiodically discarding all (sometimes only a portion) of the rinsingsolution and replacing it with fresh new solution. The determination ofthe degree of contamination of the solution has posed a problem ofconsiderable diiculty, So many possible contaminants can contribute toimpairment of the coated metal surface, especially its corrosionresistance, blister resistance and adhesion properties for appliedorganic films, that no rapid chemical tests can be expected to measureaccurately the quality of the rinsing solution.

. We have observed that, disregarding for the moment suspended solidimpurities and floating layers of organic scum, the most seriouscontaminants are the ions of s olutes contributed by dragged in coatingsolution and usually to a smaller extent, by the water supply itself.This has led to the observation that such contributions to the ionicstrength of the acid rinsing solution affect its electrical conductance.Accordingly, attempts have been made to use the electrical conductanceas a parameter capable, through suitable apparatus, of indicating theexistence of a maximum allowable, or excessive, degree of contamination.These indications have been used to operate apparatus to causeintroduction of fresh water to the bath and thus to overflow acorresponding amount of the solution whenever its conductance exceeded apredetermined level.

As a method of maintaining the solution in good operating condition,however, this method of monitoring was completely inadequate becauseconductance alone gave no indication of the amount of active ingredientspresent.

To effect suitable addition of active ingredients, then a means ofmonitoring at least one of these, say chromic acid, would be necessary.While such means are available, in theform, for instance, ofelectro-optical devices sensitive to light absorption in selectedspectral regions, such apparatus is expensive, and its use is attendedwith considerable equipment complications, such as solution circulatingcircuits for optical absorption cells, liquid filters to remove lightscattering solids, etc.

In the provision of complete automation of the controlof a phosphatingsystem of multiple stages, the control of the final acidulated rinse,though important, does not warrant the provision of both conductancecontrollers for water addition and of, say, chromate controllers withall the associated plumbing and auxiliary apparatus which would benecessary to control solution purity and effective concentration ofactive ingredients.

In accordance with the present invention, it has been found possible todevise simplified means for chemical control of acidulated rinse waterwhich function effectively to:

(a) Maintain the concentration of active chemical within suitablelimits. (b) Maintain the ionic impurity level below an allowablemaximum. (c) Minimize the occurrence of floating scum and organicimpurities.

We have found that the achievement of these goals is facilitated with amaximum of reliability and a minimum of supervision by providing acombination of means responsive to electrical signals, which willautomatically:

(a) Add separately but more or less simultaneously concentrated activerinsing chemicals, and fresh water in constant but adjustable timedincrements and ratios, independently of any signal indicating -adeparture of the quality of the rinsing solution itself from thestandard.

(b) Add both concentrated active chemical and fresh water in a constantbut adjustable ratio (preferably not greatly differing from the ratio ofactive chemical desired in the rinsing bath itself) as required torestore any lost bath volume in response to a signal received from alevel-sensing device.

(c) Add both chemical and fresh water in a constant but adjustable ratioin response to a signal generated by an increase of electricalconductive of the solution above a determined level.

In this connection, we have found that the regular periodic addition ofchemicals and water to the solution serves in great part to accommodatethe depletion of desirable ingredients and accumulations of undesirableingredients caused by relatively constant processing operations. We havealso discovered that automatic additions of water and chemicals inresponse to conductance and level measurements on the bath incombination with the periodic additions, adequately compensates forthose quality changes in the bath which build up only gradually or whichare caused by radical fiuctuations in operating conditions caused byproduction bottlenecks, break downs, unsually high throughput rates andlike circumstances.

It is an object of the present invention to provide a method andapparatus for controlling the composition of an acidulated rinse bath ofthe type employed in the treatment of metal surfaces, which method andapparatus effect the controlled addition of active chemicals and waterto the bath during use.

Another object of the present invention is the provision of a simplifiedmethod and apparatus for control 0f acidulated rinse baths whichobviates the necessity for complex and expensive automatic analyticequipment for control purposes.

A further object of this invention is the provision of acidulated bathcontrol methods and apparatus which are quite exible and adaptable tothe needs of a given metal treating operation and readily adaptable toprocessing variations which tend to occur at a given metal treatingoperation.

The above objects and purposes together with others may be more readilyunderstood by a consideration of the detailed description which followstogether with the accompanying drawings in which:

FIGURE l is a block diagram illustrating the lprincipal components ofthe invention and the flow of signals and materials between thecomponents, as applied to an acidulated rinse bath;

FIGURE 2 is a simplified diagrammatic illustration of a control systemconstructed in accordance with the invention;

FIGURE 3 is a simplified diagrammatic illustration of a control systemconstructed in accordance with the invention which offers certainadvantages when compared with the system shown in FIGURE l; and

FIGURE 4 is a simplified diagrammatic illustration of another embodimentof the invention including provision for added flexibility which may bedesirable under some circumstances.

Attention is first directed to FIGURE 1 from which an understanding ofthe basic concepts involved in the invention can be obtained. Threesources of data are utilized. One source is a timer 10, another is aconductance sensor 11, which gathers electrical conductance data fromthe acidulated rinse bath, and the third is a level sensor 12 whichgathers data concerning the level of solution in the rinse bath. l

Each of the data sources or data input means feeds data to a signalgenerator. Thus, the timer feeds data to the repeating time signalgenerator 13; the conductance sensor feeds data to the high conductancesignal generator 14, and the level sensor feeds data to the low levelsignal generator 15. The signal generators may be of various typesincluding switches and relays, and it is preferred that they at leastgenerate electrical pulse signals for use by the remaining equipment,though in some cases it may be desirable to use a generator creating asustained signal.

The signals from the three signal generators are fed to a signal shapingand routing center 16 which in its simplest form -may merelybe a set ofwiring for conveying the signals from the generators to the feedactuators. However, in the preferred embodiments the signal shaping androuting center includes equipment for converting signals from the signalgenerators into sustained signals of pre-determined time length.Preferably the center also includes equipment for creating derivativesignals related to the sustained signals in predetermined fashion, whichsignals are fed to the actuating equipment to operate it.

Concentrated chemicals are fed from a concentrated solution reservoir 17to the rinsing solution reservoir 18 through the chemical feed actuator19, which m-ay be an electrically powered pump or an electricallycontrolled valve. Similarly, water is fed from a source thereof to therinsing solution reservoir 18 through a water feed actuator 21, whichmay likewise be an electrically driven pump or an electrically operatedvalve.

In summary, the invention involves the provision and use of data inputmeans, which measure two key rinse bath parameters, and a time datainput means, all of which feed data to signal generators which in turnfeed signals to the signal shaping and routing center. Here the signalsare shaped and routed and derivative signals are fed to the electricallyoperated chemical feed actuator and water feed actuator.

. The remaining figures show specifically embodiments of equipmentarranged according to the block diagram of FIGURE 1.

In FIGURE 2, three independent switching mechanisms are indicated,respectively, by T-l, CR-l, and by the combination of elements F, R, L,SW-3 in association with the rinsing solution under chemical controlwhich is represented by WS.

In this figure T-1 represents a device which continually andrepetitively closes an electric circuit at definite `time intervals andmaintains the duration of closure as a selectable proportion of therepetition interval. For simplicity, a device of this kind will bereferred to hereinafter as a recycling proportional timer.

The secondswitching device, CR-l, represents a conductivity sensitiverelay, connected to a dipping conductivity cell D, and capable ofclosing an electrical circuit whenever the conductance of the rinsingsolution WS exceeds a value which can be pre-selected, as by varying aninternal circuit constant such as a resistance by moving a pointer overa dial.A

The third switch mechanism is represented as a float (F) operating toclose a switch SW3, via rod R, and bellcrank lever L, whenever the levelof liquid WS falls below a predetermined level. The liquid level atwhich SW-3 is operated may be adjusted by varying the length of rod R,for example. This device does not necessarily include a oat, but mayinclude a pressure sensitive switch operated by changing head of liquidin the tank or other means.

None of the individual switching elements described constitutes a newinvention per se. Each of them is commercially available or may bereadily assembled from commercially obtainable parts.

The co-action of the above three switching devices is illustrated inFIGURE 2 as follows:

Connection of the lower line of the electric mains P 6 to va commonpoint X occurs whenever any of the switches in T-l, CR-l, or SW-3 isclosed. Thus any electrical apparatus directly connected to the upperline of P and to point X is supplied with power from P.

This power may thus, for example, be supplied directly to M-2 and to V-1by connecting a terminal of each to point X, and the other terminal ofeach to the upper line of P. Y

M-Z represents a motor driving a pump Q. This pump Q is piped to areservoir containing a relatively concentrated solution of the activeingredients of the rinsing solution WS. V-1 is an electrically operablevalve in a water line connected to the Water mains or suitablereservoir. The pump Q and the water line, through V-l, deliver theircontents into suitable regions of the tank containing the solution WS.As mentioned above, an electrically operated valve can be utilized inplace o f motor M-2 and pump Q for feeding chemicals, and similarly, amotor and pump can be used in place of electrically .operated valve V-1for delivering water to the bath.

To function properly, pump M-2 and the water line through V-1 mustdeliver amounts of active ingredients and of water to WS at rates whichare accurately proportioned. Therefore, when operated directly lfrom thepower line by one or more of the associated switching means T-l, CR-l,or SW-3, the pump or other means must deliver at an accuratelydeterminable rate. It should indeed be a so-called metering orproportioning pump. The water liow likewise should be accuratelydeterminable and should ibe under the control of a ow regulator.

The recycling proportional timer causes operation of V-1 and M-2periodically to maintain the concentration of active chemical in thebath. When the level of ionic impurity rises to an objectionable'level,the conductivity sensitive device CR-l operates M-Z and' V-1 to makeadditions of water and chemicals over and above those added by theproportional timer. Additions initiated by the switching device CR-lusually continue until a certainamount `of overflow of the bath iscaused, thereby disposing of a portion of the ionic impurities.

Such overflow also carries olf floating scum and organic impurities. Wehave found that the overflow resulting from monitoring of the ionimpurity level through conductance measurements, is adequate to controlnot only the ionic impurity level, but also the level of floating scumand organic impurities. The addition of water and active chemicals inresponse to changes in the liquid level in the bath not only preventsaccumulation of undesirable ingredients because of drag-.out and partialevaporation, but prevents the undesirable depletion of desirableingredients or active chemicals. This is accomplishe-d by adding |bothactive chemicals and water in response to level changes instead ofmerely adding water as has been the prior art practice.

A more convenient arrangement, and one which requires of pump Q and thewater line through V-1 only relatively constant ow when the pump isrunning and the valve V-l is open is depicted in the diagram of FIGURE3. By this scheme only a constant, but not readily readjustable, ratioof the ows is required.

In FIGURE 3, T-2 represents a non-repeating cycle timer. T-2 comprisesthe driving synchronous motor M-l, the Variable cams D-1, D-2, and D-3,mounted on a cornmon shaft (shown dotted.) The time for each revolutionof the common shaft can be selectably adjusted by varying the gear ratioin the drive train between the synchronous motor M-l and the commonshaft, for example. Each cam operates the plunger of a switch (D-1S,D-ZS, and D-3S, respectively).

Motor M-1 is conected as shown between the upper line of power line Pand common point X of the three switching devices.

When all the switches of T-l, CR-l and SW3 are open, timer T2 is at restand all of the switches D1S,

D-2S, and D-3S are open. When any one or more of T-1, CR-l or SW-3 closemotor M-l is put in operation. As it rotates, it immediately closes allthe switches D-1S, D-2S and D-3S`. The closing of D-lS connects themotor M-l across both lines of P and assures the execution of one fullrotation of all the cams. When cam D-l has thus rotated to allow theplunger of switches D-1S to drop into the notch, thus opening theswitch, rotation of the motor and its shaft will cease, unless at thattime one or more of T-l, CR-l and SW-3 are closed, in which case themotor together with the cam assembly will again perform a completerevolution. This rotation will continue until at the time the plunger ofDAS drops into its notch, none of T-1, CR-l and SW-3 is closed. The camsystem of T-2 then remains quiescent until one of these switches againcloses, when the cycle described repeats.

During each cycle of rotation of T-2 it can be seen by reference toFIGURE 3 that switches D-2S and D-3S are closed only for the portion ofthe cycle time represented by that part of each cams circumference whichis high, i.e., which has a great enough radius to operate the plunger toclose switches D-ZS and D-3S.

The cams D-Z and D-3 are adjustable so that the relative closed times ofswitches D-ZS and D-3S are readily variable. It is thus that readilyvariable precise pumping or water flow-control is made unnecessary. Bythe arrangement ldepicted in FIGURE 3, it is only necessary to vary thesetting of either of the cams of D-2 and D-3 to effect a change in theratio of the amount of active chemical to amount of Water fed per cycleof T-2.

The advantages of the novel control method will be better understood bya review of some facts concerning a final rising stage as a part of amultistage cleaning and/or conversion coating system for metals.

(l) All of the stages of such a system comprise reservoirs for cleaning,treating or rinsing solution of a size such that rapid variation in theoverall chemical make-up in a reservoir is hardly possible.

Therefore, addition of chemical or Water to a reservoir or itsassociated circulating system need only be made at reasonableintervals-for example intervals of minutes to hours, rather thanseconds. Thus, for instance, rinsing chemical and water may be addedwithout stopping for some `fractions of a cycle time of minutes, asdictated by the operation of the cams of non-repeating timer T-2. Onlyat the end of a cycle of the timer T-2 do the dictates of the switchingmechanisms T-l, CR-l and SW-3 effect further additions of chemical andwater in the preset ratio.

(2) The concentration of the active ingredients in the acid rinsingsolution is not overly critical. Some fiuctuation of this concentrationis permissible without appreciably affecting work quality. This hascontributed to making possible the present novel, simple, reliable, andrelatively inexpensive system of control.

(3) Safety in lthe maintenance of, a low degree of contamination isvitally important even though:

(a) Some accident of processing results in a temporary high rate ofintroduction of contaminants into the rinse. (b) Evaporation or othercause leads to a decrease in volume of the rinsing solution.

(4) Although the necessary concentration of the act-ive chemical is notoverly critical, means need to \be provided to replace the activechemical continually lost by dragout" from the acid rinsing tank. Thisrestoration is accomplished by the action of repetitive timer T-1 whichinitiates the action of pump motor M-2 and water valve V-l for suitableintervals, say small fractions of an hour, sufficient toefectreplacement of solution diluted with nonactive chemical containingsolution (by drag-in or by other means). with a suitably diluted mixtureof active chemical.

To summarize, it has thus beenfound possible to correctly control withinsafe limits the composition of au acid rinsing solution of the typedescribed by the following steps:

(l) Providing a device for introducing active chemicals in concentratedform in co-action with a device for introducing water, the ratios of thefeed rates of these two devices being controllable.

(2) Both of the above devices operating under the control of switchingmeans which close together or sequentially within a predetermined timeinterval.

(3) Said switching means being, in turn, actuated directly or throughintermediate means by the closure of one or more of a group of threeinitiating switches.

(4) Said three initiating switches being closed respec- Itively by theaction of (a) a recycling proportional timer.

(b) a conductance-sensitive relay in conjunction with a conductivitycell containing the said acid rinsing solution.

(c) a level sensing device operably connected to its initiating switch.

A preferred form of the invention comprises also intermediate means foractuating the switching means which control the said devices forintroducing chemicals and water, which intermediate actuating meanscomprise one or more synchronous non-repetitive proportional timerswhose cycling is initiated by the closure of any of the said initiatingswitches and maintained so long as any of the said initiating switchesshall be closed at .the end of the cycle of one of the said timers.

As pointed out above, the concentrated chemical solution and water arepreferably added to the bath lby the control system of the invention inproportions adequate to form a replenishing stream having substantiallythe same concentration of active ingredients as the optimum activeingredient concentration of the bath. This goal is accomplished byadjusting the closure time of the cam operated switches which energizethe water valve and chemical pump with respect to each other and withrespect -to the constant delivery rates through the valve and pump. Thisadjustment is readily achieved by varying the profiles of cams D-Z andD3 of the embodiment of FIGURE 3.

We have found in some metal treating installations, so much water isdragged into the acidulated rinse tank and so much working solution isdragged out in normal operations, that Ithe addition as above outlinedof concentrated solution and water in ratio to provide a make up streamapproximately equal to the optimum bath concentration is not suflicientto keep the strength of the bath at the proper level. Nevertheless, wehave also found that simple adjustment of the chemical and wateraddition ratios to supply stronger make up solution was not a completelysatisfactory remedy. The reason for this is that when such extra strongsolutions are added in response to a signal indicating undesirably lowelectrical conductance, the high conducting make up solution causesundesirable distortion in the conductance measurements.

The embodiment of the invention shown in FIGURE 4 shows a form of theinvention which is suitable for use under the severe operatinglconditions just mentioned. In accordance with this embodiment, theconcentration of active chemicals in the make up stream is higher whenaddition of the material is initiated by the recycling proportionaltimer than it is when it is initiated by the conductance sen-sing deviceor the level sensing device. Thus, under the lpreferred mode ofoperation of this embodiment the make up solution added in response tothe recycling proportional timer signals is enough stronger than theoptimum concentration of lthe rinse bath to restore the depleted activechemical which is lost because of drag-in of water vand drag-out ofsolution. We have found that the repetitive timer signal is lthe bestinitiator for adding extra `strong make up solution Abecause thedepletion caused by drag-in and drag-out occurs at a fairly constantrate and the addi-tions in response to the repetitive -timer signals,when integrated over a period of time, are also achieved at a fairlyconstant rate.

The additions of make up material in response to signals from theconductance sensor and the level sensor in the embodiment in FIGURE 4are at a concentration approximately equal to the desired bathconcentration and thus at a lower concentration than the timer initiatedadditions. t

In FIGURE 4, the parts which correspond to parts also employed in theembodiments of the earlier gures are given in the same referencecharacters. Thus, the acidulated rinse bath is indicated at WS. It isequipped with a oat F, having a rod R which cooperates with lever L tooperate Switch SW-3. Similarly, the bath is equipped with a conductancemeasuring cell D connected to a conductivity sensitive relay CR-l. TheValve V-1 is again located in the water feed line and motor M-Z drivespump Q in the chemical feed line.

Timers T-l and T-2 are modified in this embodiment as compared to theembodiment of FIGURE 3. Timer T-l in FIGURE 4 is equipped with a relayRY having three normally open contacts RY-l, RY-Z and RY-3. The relay isenergized upon closure of the switch of timer T-1, and upon beingenergized closes contacts The non-repetitive time-r T-Z in FIGURE 4-ismodified in that the cam shaft of motor M-l now carries tive adjustablecams D-1 through D-5 instead of three such cams. There are alsolprovided ve cam-operated switches D-1S through D-SS, one for each cam.In FIGURE 4, cam D-1 and its switch D418 again function to provideelectrical power to motor M-1 after it has been started by closure ofeither the switch of timer T-'1, the switch of conductivity sensitiverelay CR-l, or level sensitive switch SW-3. Thus, cam D-l and its switchassure that motor M-l will operate through one full revolution of thecam shaft.

Cam D-2 and its switch D-2S cooperate to energize Velectrically operatedValve V-1 during a portion of the rotation of the cam shaft. Cam D3 andits switch D-3S are arrangedto energize motor M-2 which drives thechemical feed pump for a portion of a revolution of the cam shaft.

Cam D-4 and its switch D-4S are also arranged to energize motor M-2 Oneside of switch D4S is connected to motor M-2 and the other side lisconnectable through relay contact RY-S to the low side of the power lineP. Cam D isproled so that it will hold D-4S closed for longer portion ofa revolution of the cam shaft than f cam D-3 vwill hold switch D-3Sclosed. Thus, if relay contact RY-3 is closde, D-4S will energize motorM-2 for a longe-r time period during each cycle than will switch D-3S;on the other hand, 'if` relay contact RY3` is open, closure of switchD-4S will not energize motor M-Z.

Cam D.-5 is positioned to hold switch D-SS closed f during most of arevolution of t-he cam shaft. Cam D5 can be proled substantially likecam D-l if it is desired, and for reasons whichwill appear below, it ispreferred that .the high portion of cam D-S atleast cover as large anangle as the high portion of cam D-4, and that the low portion of cam D5coincide, .at least in part, with the low portion of cam D-l.

In operation the embodiment of FIGURE 4 functions as additions of waterand chemicals in response to conductivity signals and level signals isconcerned. Thus, closure of conductivity relay CR-l or level sensitiveswitch SW-S will causel timer T-Z to rotate for one full revolution.During the revolution, switches lD-ZS and D3S are held -closed by camsD-2 and D-3 respectively. Motor M-2 and valve V-1 are operated to effectaddition of chemicals and water.

The action of the control equipment of FIGURE 4 in response to timer T-1differs from the embodiment of FIGURE 3. In FIGURE 4, when the switch oftimer quite similarly to the embodiment of FIGURE 3 as far T-1 closes,relay RY pulls in, thus closing contacts RY1, RY-2, and RY-3. Power isdelivered to motor M-1 through relay contact RY-l, and the timer T-Zthus begins to rotate. It will rotate at least through one fullrevolution since cam D-1 holds switch D-lS closed throughout arevolution. As timer T-Z rotates, cam D-S closes switch D-SS, and thisresults in the relay RY remaining energized for so long as cam D-S holdsD-SS closed, even if the switch of timer T-l opens.

At this point it should be noted that relay contact RY-3 is held closedso long as relay RY is energized. Relay contact RY-3 supplies power toone side of switch D-4S, the other side of which is connected to motorM-2. Thus, when switch D-4S is closed by cam D-4, power is available foroperating motor M-2 so long as relay contact RY-3 is closed. Cams D-4and D-5 both have profiles such that they close their respectiveswitches for a greater portion of a revolution of timer T-2 than cam D-3closes its switch. This means that when the timex- T-l initiates arevolution of timer T-Z, power is delivered to motor M-2 for a longerperiod than when timer T-Z is operated by CR-l or SW3. Thus,concentrated chemical will be added to the bath for a greater portion ofeach cycle of timer T-2, and since valve V1 is opened for the sameamount of time by switch D-2S regardless of how timer T-Z is started,the ratio of chemicals to water for a cycle initiated by timer T-1 isgreater than the ratio in a cycle initiated by CR-l or SW-3.

The proles of cams D1 through D-5 may readily be adjusted in knownmanner so that relative rates o f addition of chemical and water undercommands from CR-1 and SW-3 on the one hand and timer T-l on the otherhand may be varied to meet the requirements of a particularinstallation. These adjustments can be accomplished at a central consolewhere timer T-Z may be located, thus eliminating the necessity formaking adjustments at the pumps and valves.

We claim:

1. A device for controlling the composition of an acidulated rinse bathof the type employed in the treatment of metal sur-faces, by thecontrolled addition of active chemicals and water to the bathcomprising: an electric motor driven pump for delivering concentratedsolution of active chemicals from a supply thereof to said bath, anelectrically controlled valve for delivering Water from a sourcethereof-to said bath switch means for electrically energizing said pumpand said valve upon closure of said switch means, a cycle timer havingswitch operating elements for said switch means, and having timing meansresponsive to switch actuation thereof to maintain said timer inactivated condition throughout a timed cycle of operation, and aplurality of means for initiating activation of said cycle timercomprisingv a timer switch operated at timed intervals by a recyclingproportional timer, a conductivity sensitive switch operatedv by anincrease of the electrical conductivity of the bath above apredetermined value, and a liquid level sensitive switch operated by afall of the level of the bath below a predetermined value, each of theswitches of the means for initiating activation ofthe cycle timer beingconnected between a source of electrical energy and with said cycletimer.

2. A device for controlling the composition of an acidulated rinse bathof the type employed in the;treat ment of metal surfaces, by thecontrolled addition of active chemicals and Water to the bathcomprising: electrically operable chemical feed means for deliveringconcentrated solution of active chemicals` from a supply thereof ltosaid bath, electrically operable water feed means for de# livering waterfrom a source thereof to said bath, conf trol switch means forelectrically energizing said feed means` upon closure of said controlswitch means, a synchronous cycle timer having timing switch means formaintaining said timer in activated condition for a predetermined timefollowing activation thereof, and having comprising a conductivitysensitive device including a conductance cell, a switching relayactuated by said conductance cell and including circuit means forvarying the value of bath conductance as measured by said cell effectiveto a-ctuate said switching relay, and a float actuated liquid levelsensitive switch operable upon fall of the level of the bath below apredetermined value, each of said activating means being connectedbetween a source of electrical energy and said cycle timer, supplementalcontrol switch means for electrically energizing said chemical feedmeans, a supplemental cam on said cycle timer output shaft for actuatingsaid supplemental control switch means, a recycling proportional timerhaving a multicontact switching relay actuated by said proportionaltimer at predetermined intervals, one contact of said multicontactswitching relay being connected between a source ofelectrical energy andsaid cycle timer, another contact of said multicontact switching relaybeing connected between a source of electrical ener-gy and saidsupplemental control switch means, and holding means for saidmulticontact switching relay for holding it in actuated condition for apredetermined time upon actuation thereof,

3. A device in accordance with claim 2 in which said holding meanscomprises holding switch means connected ybetween said multicontactrelay and a third contact of said multicontact relay, said third contactbeing connected to a source of electrical energy, and a secondsupplemental cam on said cycle timer output shaft for actuating saidholding switch means.

4. A device for controlling the composition of an 'acidulated rinse bathof the type employed in the treatment of metal surfaces, by controlledaddition of active chemicals and water to the bath comprising:electrically operable chemical feed means for delivering concentratedsolution of active chemicals from a supply thereof to said bath,electrically operable water feed means for delivering water from asource thereof to said bath, control switch means for electricallyenergizing said feed means upon closure of said control switch means, asynchronous cycle timer having timing switch means for maintaining saidtimer in activated condition -for a predetermined time followingactivation hereof, having an output shaft carrying a first cam foractuating said timing switch means, and further having second and thirdcams on said shaft for actuating said control switch means, and pluralactivating means for said synchronous cycle timer comprising a recyclingproportional timer, a conductivity sensitive 'device including aconductance cell, a switching relay actuated by said conductance celland including circuit means for varying the value of bath conductance asmeasured by said cell effective to actuate said switching relay, and afloat actuted liquid level sensitive switch operable upon fall of thelevel of the bath below a predetermined value, each of said activatingmeans being connected between a source of electrical energy and saidcycle timer. 5. A device for controlling the composition of anacidulated rinse bath of the type employed in the treatment of metalsurfaces, by the controlled addition of active chemicals and water tothe bath comprising: electrically operable chemical feed means fordelivering concentrated solution of active chemicals from a supplythereof to said bath, electrically operable water feed means fordelivering water from a source thereof to said bath, control switchmeans for electrically energizing said feed means upon closure of saidcontrol switch means, a synchronous cycle timer having timing switchmeans for maintaining said timer in activated condition for apredetermined time following activation thereof, having an output shaftcarrying a first cam for actuating said timingswitch means, and furtherhaving second and third cams on said shaft for actuating said controlswitch means, and plural activating means for said synchronous cycletimer comprising a recycling proportional timer, a conductivitysensitive device including a conductance cell, a switching relayactuated by said conductance cell and including circuit means forvarying the value of bath conductance as measured by said cell effectiveto actuate said switching relay, each of said activating means beingconnected between a source of electrical energy and said cycle timer.

6. A device for controlling the composition of an acidulated rinsebathof the type employed in the treatment of metal surfaces, by thecontrolled addition of active chemicals and water to the bathcomprising: electrically operable chemical feed means for deliveringconcentrated solution of active chemicals from a supply thereof to saidbath, electrically operable water feed means for delivering water from asource thereof to said bath, control switch means for electricallyenergizing said feed means upon closure of said control switch means, asynchronous cycle timer having timing switch means for maintaining saidtimer in activated condition for a predetermined time followingactivation thereof, having an output shaft carrying a first cam 4foractuating said timing switch means, and further having second and thirdcams on said shaft for actuating said control switch means, and pluralactivating means for said synchronous cycle timer comprising a recyclingproportional timer, and a float actuated liquid level sensitive switchoperable upon fall of the level of the bath below a predetermined value,each of said activating means being connected between a source ofelectrical energy and said cycle timer.

7. A device for controlling the composition of an acidulated rinse bathof the type employed in the treatment of metal surfaces, by thecontrolled addition of active chemicals and water to the bathcomprising: electrically operable chemical feed means for deliveringactivechemicals from a supply thereof to said bath, electricallyoperable water feed means for delivering water from a source thereof tosaid bath, signal generating means for initiating operation of said feedmeans comprising a repeating time signal generator, a high conductancesignal generator, and a low level signal generator, data input means foreach of said signal generating means comprising a timer for deliveringtime data to said time signal generator, an electrical conductancesensor positioned in said bath for delivering conductance data to saidhigh conductance signal generator, and a liquid level sensor positionedin said bath for delivering liquid level data to said lofw level signalgenerator, and signal shaping and routing means electrically interposedbetween said signal generating means and said feed means, includingmeans for converting a signal from any of said signal generating meansinto a sustained signal of predetermined time length, means forconnecting said chemical feed means to a source of electrical energy,means for connecting said water feed means to a source of electricalenergy, and means for actuating said connecting means for predeterminedfractions of the time length of said sustained signal.

References Cited UNITED STATES PATENTS 2,787,281 4/1957 Word 137-52,874,714 2/1959 Pellerin 137-5 3,073,330 1/1963 Fattor 137-93 3,095,1216/1963 Douty 137--93 3,195,551 7/1965 Russell 137-5 3,292,650 12/1966Bird 137--93 WILLIAM F, ODEA, Primary Examiner.

W. WRIGHT, Assistant Examiner.

